Damage to the spine as a result of advancing age, disease, and injury, has been treated in many instances by fixation or stabilization of vertebrae. Conventional methods of spinal fixation utilize a rigid or semi-rigid spinal fixation device to support an injured spinal vertebra relative to an adjacent vertebra and prevent movement of the injured vertebra relative to an adjacent vertebra. These conventional spinal fixation devices include anchor members for fixing to a series of two or more vertebrae of the spine and at least one substantially rigid link element designed to interconnect the anchor members. Typically, the anchor member is a screw and the substantially rigid link element is a rod. The screw is configured to be inserted into the pedicle of a vertebra to a predetermined depth and angle. One end of the rigid link element is connected to an anchor inserted in the pedicle of the upper vertebra and the other end of the rod is connected to an anchor inserted in the pedicle of an adjacent lower vertebra. The rod ends are connected to the anchors via coupling constructs such that the adjacent vertebrae are supported and held apart in a relatively fixed position by the rods. Typically, two rods and two pairs of anchors are installed each in the manner described above such that two rods are employed to fix two adjacent vertebrae, with one rod positioned on each side of adjacent vertebrae. Once the system has been assembled and fixed to a series of two or more vertebrae, it constitutes a rigid device preventing the vertebrae from moving relative to one another. This rigidity enables the devices to support all or part of the stresses instead of the stresses being born by the series of damaged vertebra.
The implantation of a rod requires a pathway to be created through the surrounding tissue between two anchors. Because of the surrounding tissue between two anchors is comprised of muscle and fascia, the pathway, if not cleared, makes passing the rod through muscle and fascia quite difficult. Therefore, there is a need for instrumentation designed to create a pathway for rod implantation. Furthermore, in minimally invasive procedures, the pathway preferably needs to be cleared subcutaneously to minimize the disruption and damage to the surrounding tissue. Therefore, the need extends to instrumentation designed to create a pathway subcutaneously for rod implantations. The present invention sets forth such instrumentation.